The recently introduced Stop Online Piracy Act has ignited a firestorm of protest from numerous quarters. Many of those opposed to the bill see in it a cynical attempt by the entertainment industry to impose a sort of Internet censorship regime. Supporters downplay that criticism and say the bill is needed to counter the theft of hundreds of billions of dollars worth of U.S. IP annually. Here's what the big fight is all about.

What is SOPA? SOPA is an acronym for the Stop Online Piracy Act ( H.R. 3261 ). It is a bill designed to make it much harder for rogue offshore sites to sell counterfeit U.S. goods, including fake prescription drugs and copyrighted movies and music. Such sites are believed to be causing tens of billions of dollars in losses annually to U.S. companies.

If stopping rogue offshore websites is a good thing, why are so many people upset? Because they believe the proposed cure is worse than the illness. Many fear that SOPA will give content owners and IP owners too much power to go after websites that they deem are dedicated to or contributing to copyright theft or sale of counterfeit goods.

Why do they feel that way? Primarily because of Section 103 of the bill, which deals with a market-based system designed to prevent U.S. funding of sites seen as dedicated to the theft of U.S. property.

Try that again. Basically, Sec. 103 will give the owner of any intellectual property the right to pursue private action against websites that they deem are infringing their rights. Under SOPA, IP rights holders will be able to ask payment providers such as MasterCard and PayPal to shut off services to allegedly infringing sites. They would also be able to ask Internet advertising networks to stop providing ads to the websites.

Don't IP owners need some a court order before they ask ISPs and the others to do this? Not really. ISPs will get five days to use all "technical feasible and reasonable" measures to voluntarily comply with the request. Those that do will get full immunity from any liability. Those that don't can be forced to do so under court order.

Is this the only concern with the bill? SOPA also would allow the government to ask ISPs to use DNS blocking, filtering and other "feasible and reasonable" methods to cut off access to foreign infringing websites from the U.S. It would let the government order search engine companies like Google to disable links to infringing sites in search engine results and ask payment providers to stop services to targeted sites. Foreign sites subject to such actions are those that would have been liable for criminal prosecution in the U.S if the site were based in the U.S.

Really, isn't this the most effective way to deal with rogue offshore sites? Since most are outside the reach of U.S. law enforcement, it may well be. But the problem, according to critics, is that SOPA is worded in a way that leaves U.S. companies wide open to similar actions from content owners. The bill refers to "U.S.-directed" websites. That term can apply to any and every site that can be accessed by a U.S.-based user. So, in theory, at least, a YouTube or a Flickr or an EBay could be targeted by content owners for carrying copyrighted content.

But doesn't the Digital Millennium Copyright Act (DMCA) grant immunity to website owners for content posted by users? Yes, it does. The DMCA offers website owners a Safe Harbor for content posted on their site by users. So, YouTube for instance cannot be held responsible if one of its users posts copyright infringing material on its site. DMCA allows content owners to ask the YouTubes of the world to take down infringing material. But they cannot sue the site itself unless it refuses.

So U.S. websites are protected from SOPA then? Not really. Critics contend that SOPA will let content owners do an end-run around DMCA. With SOPA, content owners need not bother with takedown notices. They can target an entire website if they choose to.

That's just FUD, isn't it. Supporters of the bill insist that SOPA is targeted mainly at the worst of the worst offshore rogue websites. The bill describes such sites as those that are "primarily designed or operated" for the purpose of offering infringing and counterfeit goods and services and little else. That definition would seem to exclude sites that may occasionally carry an infringing item or two, but are not dedicated to copyright theft and counterfeiting.

What recourse do targeted websites have? The law will offer targeted websites between five and seven days to explain why they should not be subject to the prescribed action. Relief for targeted websites will be available in accordance with Federal Rules of Civil Procedure. But the operators of such foreign sites will first need to agree to be subject to U.S. laws.

What other protections do accused sites have? The bill would require content owners to provide ISPs, payment providers and others with detailed written explanations, supported by proof, of why they are seeking action against the sites.

Who's behind SOPA? SOPA was introduced in the U.S. House of Representatives by Lamar Smith (R-Va.). It is co-sponsored by John Conyers (D-Mich.), Bob Goodlatte (R-Va.), Howard Berman (D-Calif.) and several other lawmakers. The bill enjoys support from the U.S. Chamber of Commerce and predictable quarters such as the Motion Picture Association of America and the Recording Industry Association of America. It also has garnered wide support from a majority of state attorneys-general, law enforcement officials, hundreds of trade unions and industry groups, and even a few companies such as Pfizer.

So who, then, is really opposed to it? Lots of people, including free speech and rights advocacy groups, industry associations, academicians, lawyers and some of the largest web companies, including Google, Yahoo, Facebook and others.

So what happens to SOPA next? The House Judiciary Committee held a hearing on it on Wednesday, and it's expected to go to legislative "mark-up" by the end of the year. Exactly when it comes to a vote is unclear.